Work machines such as excavators, backhoes, front shovels, and the like are used for excavation work. These excavating machines have work implements which consist of boom, stick and bucket linkages. The boom is pivotally attached to the excavating machine at one end, and to its other end is pivotally attached a stick. The bucket is pivotally attached to the free end of the stick. Each work implement linkage is controllably actuated by at least one hydraulic cylinder for movement in a vertical plane. An operator typically manipulates the work implement to perform a sequence of distinct functions which constitute a complete excavation work cycle.
In a typical work cycle, the operator first positions the work implement at a dig location, and lowers the work implement downward until the bucket penetrates the soil. Then the operator executes a digging stroke which brings the bucket toward the excavating machine. The operator subsequently curls the bucket to capture the soil. To dump the captured load the operator raises the work implement, swings it transversely to a specified dump location, and releases the soil by extending the stick and uncurling the bucket. The work implement is then returned to the trench location to begin the work cycle again. In the following discussion, the above operations are referred to respectively as boom-down-into-ground, dig-stroke, capture-load, swing-to-dump, dump-load, and return-to-dig.
The earthmoving industry has an increasing desire to automate the work cycle of an excavating machine for several reasons. Unlike a human operator, an automated excavating machine remains consistently productive regardless of environmental conditions and prolonged work hours. The automated excavating machine is ideal for applications where conditions are dangerous, unsuitable or undesirable for humans. An automated machine also enables more accurate excavation making up for the lack of operator skill.
Therefore, it is desirable to "teach" the automatic control the excavating work cycle as defined by the operator so that the automatic control may perform the work cycle. However, rather than simply repeat the work cycle, it may be desirable to modify the work cycle according to changes in the excavating environment to perform efficient excavating.
The present invention is directed to overcoming one or more of the problems as set forth above.